Lithium Disilicate

[TheLabGuy]

I've got a question/comment about strength.

YZ runs around 1200 Mpa, Empress Esthetic around 140 Mpa, Lithium Disilicate around 400 Mpa.

Now tell me if i'm correct, Porcelain is as only strong as the strength between the porcelain and substructure. Now on YZ, the porcelain on the YZ is only 90 Mpa. Empress Esthetic stays the same 140 Mpa. Lithium Disilicate is also the same at 400 Mpa. Making Lithium Disilicate stronger than anything on the market. Now I know the YZ substructure is stronger, but it's weak between the porcelain and YZ substructure (90 Mpa).

Please tell me your thoughts, because what I've seen from most labs and techs for that matter is that they are seriously confused about this and think Zirconium, YZ, In-Ceram is the strongest thing out there, when technically, they're factually wrong. Unless I'm wrong............maybe?

[Al.]

Rob, I thought the strength value of zirconia was around 900 mpa?

I press all my posteriers full contour and layer the incisal 1/3 of upper bi's. in LD.
Anything less then .8 clearance I reduce the opposing.
For strength Id put one of these up against a milled yz coping that is layered anyday, but its a different story if I press a coping in LD and then layer it. But there is really no need to layer anything more then the incisal with the LT ingots.
Ive done plenty of posterior bridges in Lithium Disilicate with no fractures to date. As long as I have plenty of room for strong connections it would take a brute to break them.

It would be intresting to see a strength test on a 4mm pressed rod of 100% LD vs a 2mm milled rod of yz with 2mm of layered porcelin built around it.

[labdude]

They could be factually right, or maybe wrong technically. I don't think your wrong factually, technically maybe slightly, maybe....
I don't know for sure. I have no factually correct or technically true facts on the issue, I don't think, maybe.

[Al.]

Originally Posted by labdude

They could be factually right, or maybe wrong technically. I don't think your wrong factually, technically maybe slightly, maybe....
I don't know for sure. I have no factually correct or technically true facts on the issue, I don't think, maybe.

Dang, you got me plum befuddled.

[sixonice]

Originally Posted by TheLabGuy

I've got a question/comment about strength.

YZ runs around 1200 Mpa, Empress Esthetic around 140 Mpa, Lithium Disilicate around 400 Mpa.

Now tell me if i'm correct, Porcelain is as only strong as the strength between the porcelain and substructure. Now on YZ, the porcelain on the YZ is only 90 Mpa. Empress Esthetic stays the same 140 Mpa. Lithium Disilicate is also the same at 400 Mpa. Making Lithium Disilicate stronger than anything on the market. Now I know the YZ substructure is stronger, but it's weak between the porcelain and YZ substructure (90 Mpa).

Please tell me your thoughts, because what I've seen from most labs and techs for that matter is that they are seriously confused about this and think Zirconium, YZ, In-Ceram is the strongest thing out there, when technically, they're factually wrong. Unless I'm wrong............maybe?

I believe you are 100% correct and I agree with you. Here is my slice: True, Zirconia substrates are super strong (900-1000mpa depending on what you read). On a layered zirconia, you are correct the weak point is the interface between the zirconia and the build up of glass (90 mpa-like you said). Failures would come in the form of delamination of the ceramic off the zirconia. Now take a Lithium Disilicate, full press at 400mpa, no interface. Both are conventionally cemented. For single units its a no-brainer-the Lithium Disilicate would be better (and MUCH more profitable for the lab!!) Its like comparing 2 bricks that have mortar in between them versus a SOLID brick with no mortar. Zirconia shines on long span anterior bridges and posterior bridges. The substructure design is aso vital in zirconia, where proper support must be adhered to to give the layering ceramic proper support.

[TheLabGuy]

Originally Posted by sixonice

On a layered zirconia, you are correct the weak point is the interface between the zirconia and the build up of glass (90 mpa-like you said).

Its like comparing 2 bricks that have mortar in between them versus a SOLID brick with no mortar.

Great explanation with an awesome analogy. Thanks a bunch sixonice, once again, you came threw like a champ!!!!!!

[sixonice]

Glad I could help Labguy! It was funny, I was trying to think up of a cool analogy that could help all you guys get a good "picture" in your mind on the differences. I just think doing single units of zirconia is too expensive doesn't matter whether you mill it in your own lab or send it out to get milled)-save it for the longer bridges.

[Al.]

Originally Posted by sixonice

I just think doing single units of zirconia is too expensive doesn't matter whether you mill it in your own lab or send it out to get milled)-save it for the longer bridges.

You got that right!
It seems like all the trade magazines are trying to shove $75,000 milling units down our throats like their the cats meow of dentistry.
Ive out sourced a few maryland bridges. Close to $300 for one pontic and 2 wings.